Apparatus for gaseous treatment of moving webs



5, 1970 E. c. BROWN 3,525,164

APPARATUS FOR GASEOUS TREATMENT MOVING WEBS 2 SheetS-Sheet 1 FIG FiledDec. 10, 1968 I IZ FIG 2 E. C. BROWN Aug. 25, 1970 I APPARATUS FORGASEOUS TREATMENT OF MOVING WE BS 2 Sheets-Sheet 2 Filed Dec. 10, 1968,A MW) FIG 5 United States Patent 3,525,164 APPARATUS FOR GASEOUSTREATMENT OF MOVING WEBS Ernest Charles Brown, Danvers, Mass., assignort0 Wolverine Corporation, Woburn, Mass., a corporation of MassachusettsFiled Dec. 10, 1968, Ser. No. 782,620

Int. Cl. F26b 23/00 US. Cl. 34-155 Claims ABSTRACT OF THE DISCLOSUREApparatus for gaseous treatment of moving webshas a plenum embracingparallel spaced exhaust cross-headers with the spaces between thecross-headers forming outlet passageways from the plenum leading tolower level perforate distributing heads between which are verticalexhaust passageways leading to the exhaust cross-headers so that airimpacting on the moving web is drawn away from the moving we b beforemoving transversely through the cross-headers to discharge points beyondthe edges of the moving web.

This invention relates to apparatus useful in the gaseous treatment ofmoving webs, as for drying wet coatings applied to a sheet material.

Some coatings, for example, those applied to non-porous substrates inthe manufacture of photographic film are so thin and fragile that dryingthe coatings with any substantial forced draft directed towards thecoating tends to disperse the coating and fails to produce desired evencoating. Yet contact of the material to be dried with a gaseous dryingmedium having movement relative to the coated surface is desired inorder to speed up the drying operation as much as is possible so long asthe coating dries uniformly in an even coat, for the greater thequantity of gas contacting the material per unit of time the faster thedrying.

The difficulty is that, as the velocity of a gaseous drying medium isreduced to prevent disruption of the coating, so much of the potentialenergy comes to bederived from turbulence alone (it being impossiblebecause of skin and other effects to have truly laminar flow) that theflow is not uniform cross-sectionally. Energy derived from turbulence isdispersed randomly as distinguished from energy derived from staticpressure which is dispersed evenly. In some applications then the slightstatic pressure required for low velocity gas movement contributes solittle energy that the total force applied to the medium barely exceedsthe force which would anyway be present due to turbulence alone. Theresult is that the velocity of gas movement varies at different pointsof impact on the web causing non-uniform drying over the surface area.

In a structure such as is shown and described in my Pat. No. 3,398,466,for example, if the velocities at the slots 39 are reduced below 500feet per minute, most of the potential energy is derived fromturbulence, and there is such little control of the exhausting gases inthe spaces around the plenum 12 that a web being treated receivesimpacts at randomly varying velocities and uniform drying across the webis not achieved.

The present invention provides an air distributing structure which isparticularly useful in drying moving webs which can tolerate only verylow velocity gaseous impact, e.g., at velocities below 500 linear feetper minute, although the structure can be useful for operations athigher velocities. By using cross-headers within a plenum for exhaustingthe gases rather than cross-headers outside the plenum for the ingoinggas, I have found that so much better control of the exhaust gases issecured as to elimiice nate random variation in velocity of low velocitygas at impact, at least so far as can be determined from finished driedproducts. Accordingly, I expose a distributing head to the staticpressure of a gas in a plenum which embraces a series of spaced exhaustcross-headers. Additionally, in accordance with this invention, aresistance distributing head in the form of a perforated plate is placedacross each plenum outlet passageway between the exhaust head ers andthese passageways then communicate with lower distributing heads in theform of perforated plates which are less open than the upper plates.

In this manner the pressure in the plenum maybe considerable while thepressure between the plates is less and such as to produce a very gentlelow velocity draft of extremely evenly distributed impact with muchincreased velocity at the ingress to the exhaust headers.

The structure is also much simplified because tubes, such as are used inUS. Pat. No. 3,398,466 are no longer required,

Apparatus in accordance with the present invention is shown in thedrawings wherein:

FIG. 1 is a perspective view of the apparatus with one wall broken awayto illustrate internal features;

FIG. 2 is a transverse cross-sectional view taken through a passagewayin the apparatus of FIG. 1, leading downwardly from a plenum;

'FIG. 3 is a transverse cross-sectional view taken through an exhaustpassageway in the apparatus of FIG. 1 leading upwardly to an exhaustheader;

FIG. 4 is a perspective enlarged view of some portions of the apparatusin an upwardly tilted position; and

FIG. 5 is a longitudinal cross-sectional fragmentary view showing theconstruction of the composite bottom Wall of the plenum.

The apparatus includes an enclosure 10 through which may be carried, ason appropriate rollers 12 and 14, by virtue of conventional inlet andoutlet openings 16 and 18, respectively, a web or film W of coatedmaterial to be dried.

Superposed over the web is an air distributing system which, forconvenience, will be described from the bottom up and as best can beseen in FIG. 4. A series of transverse one-piece members 20 aresupported in spaced relation across the enclosure above the path of theweb W. Each member 20 includes a horizontally extending portion 22having perpendicularly disposed appendages in the form of a pair ofspaced parallel vertical walls 24 spaced inwardly from the side edges ofthe member 22, one on each side of a row of openings 26 through theportion 22.

Both side edges of members 22 have slots 28 formed therein into whichmay be inserted, between each member 20, a perforated plate 30connecting the members 20 together.

, Vertical walls 24 also terminate at the bottom in enlargements inwhich similar slots 34 are provided into which may be insertedintervening perforated plates 36 connecting the bottoms of the adjoiningwalls 24 of adjacent members 22 together.

Lastly, one-piece members 20 have on their upper faces vertical slots 38extending along each side thereof for receiving inverted U-shapedhousings 40 forming with the portions 22 crossheaders communicatingthrough openings 26 with exhaust passageways 42 formed between each pairof walls 24.

As shown in FIG. 3, the cross-headers 40 lead to an outlet 44 disposedbeyond the side edge of the path of the travelling web to be treated.

The enclosure 10 above and surrounding the crossheaders 40 thus forms aplenum 50 having top inlets 51 and communicating with the spaces 52forming vertical passageways between cross-headers 40.

A fan or other conventional air mover 54 is placed in the cross-headeroutlets 44 to create a differential pressure between air in plenum 50and in the cross-headers 40 thereby creating air flow from plenum 50down through vertical passageways 52, through apertured plate 30,through apertured plate 36 against the web W, the air then travellinglongitudinally of the web symmetrically to and up the exhaustpassageways 42 between walls 24, through openings 26 and into thecross-headers 40.

The configuration of the bottom wall of the plenum can thus be describedas being a series of hollow boxes connected together in staggeredrelation in upper and lower rows, the upper row boxes being defined bywalls 40 and 22 and the lower row boxes by walls 24 and interveningupper and lower plates 30 and 36. The bottom walls 22 of the upper rowboxes have openings 26 and both top and bottom walls 30 and 36 of thelower row boxes have openings therein, being perforated.

The perforations in plate 30 are larger than those in plate 36 but plate36 may have, for example, 22.5% open area and plate 30, 90% open area ina construction wherein the passageways 52 are 3 inches wide and theexhaust passageways 42, 1 inch wide. This gives a five to one ratio oftotal open area between the upper plate 30 and the lower plate 36.Accordingly, in operation, if the pressure in the plenum is of the orderof .25 to .76 inch water column, the static pressure between the plateswill be of the order of .01 and .03 inch water column. The exhaust gasat openings 26 may then have a velocity of 2300 to 4000 feet per minutewith an intake at plate 30 of about 2000 to 3500 feet per minute. Thisprovides a flow from plate 36 in the order of between 72 and 126 cubicfeet per minute where the passageways 52 and 42 are five feet longtransversely of the apparatus.

It is to be understood that in some cases where extremely low velocitiesare not required, the plate 30 may be dispensed with entirely and ofcourse it will be under stood that by virtue of the slot constructionfor insertion of the plates 30 and 36, they may be readily replaced withplates having varying open areas and/or size of perforations dependingupon the type of operation desired. In the form shown, the apertures 26are inch in diameter, the apertures in plate 30, inch in diameter andthe apertures in plate 36, V inch in diameter. Also, the slots in themembers 20 are not essential to the invention since the plates may beotherwise supported, nor is it essential that the members 20 be of onepiece construction, though when they are and are fabricated byextrusion, assembly is conveniently simple.

What is claimed is:

1. Apparatus for gaseous treatment of moving webs comprising wallsforming a plenum,

one of the walls of said plenum being a horizontally extending compositewall which includes:

spaced transverse vertical walls forming therebetween an outer alignedrow of parallel vertical passageways,

a series of spaced hollow cross-headers, each spanning the inner end ofan alternate passageway of said row and having intake openingscommunicating therewith and having an end outlet for discharging airoutside of said plenum,

said headers forming therebetween inner extensions of the interveningvertical passageways in said outer row, and forming therewith outletpassageways from said plenum,

a series of perforate plates, each spanning one of said outletpassageways for distributing gas passing therethrough, and

means for maintaining a differential lower pressure in said headers thanin said plenum to draw gaseous fluid continuously from said plenumthrough said outlet passageways against a web passing beneath saidcomposite wall, around free edges of said vertical walls into thealternating outer vertical passageways and thence through said intakeopenings into the cross-headers and thence to said cross-header outletsfor discharge outside said plenum beyond the path of said moving web.

2. Apparatus as claimed in claim. 1, wherein said crossheaders are widerthan said alternate outer row passagewaysand said plenum outletpassageways have narrow inner portions between said headers and widerouter portions between said vertical walls.

3. Apparatus as claimed in claim 1, wherein said perforate plates lie ina single plane intersecting the outer ends of said plenum outletpassageways.

4. Apparatus as claimed in claim 1, wherein said series of perforateplates include an outer and an inner plate spanning each plenum outletpassageway.

5. Apparatus as claimed in claim 4, wherein the perforations in saidinner plates are larger than the perforations in said outer plates.

6. Apparatus as claimed in claim 2, wherein said series of perforateplates include outer plates lying in one plane across said wider Outerportions of said plenum outlet passageways and inner plates lying in adifferent plane across said narrow portions of said plenum outletpassageways.

7. Apparatus for gaseous treatment of moving webs comprising wallsforming a plenum,

one of the walls of said plenum being a horizontally extending compositewall which includes a series of hollow boxes connected together instaggered relation in upper and lower rows, the boxes in each row beingspaced from one another longitudinally of said plenum,

the bottom walls of the boxes in said upper row having openings thereincommunicating with the spaces between the boxes in the lower row,

the top walls of the boxes in the lower row having openings thereincommunicating with the spaces between the boxes in the upper row,

the bottom walls of the boxes in the lower row being perforated,

and means for maintaining a differential lower pressure in said upperrow of boxes than in said plenum to draw gaseous fluid continuously fromsaid plenum through said lower row bottom wall perforations against aweb passing beneath said composite wall and then away from said webthrough said openings in the bottom walls of the upper row boxes intosaid upper row boxes and then laterally through said upper row boxes fordischarge beyond the path of said moving web.

8. Apparatus as claimed in claim 7, wherein said boxes in the upper andlower rows symmetrically partially overlap one another.

9. Apparatus as claimed in claim 7 wherein the openings in the top wallsof the boxes in the lower row are perforations in the portions of saidtop walls lying between said boxes in the upper row.

10. As a composite plenum wall, a series of one-piece strgctural membersarranged in parallel spaced relation, an

perforated plates extending between said members,

each of said one-piece members comprising:

an elongated plate having a series of medially aligned openings,

a pair of parallel spaced legs extending from one side of said platenormal to said plate, one on each side of said series of openings, butspaced inwardly from the longitudinal side edges of said plate,

said legs including portions defining oppositely outwardly facing slotsextending along the marginal bottom edge portions of said legs slidablyreceiving 8,525,164 5 6 and supporting one edge of adjacent perforatedand outwardly of a plenum of which said composite plates, and wall formsone wall. marginal edge portions of said plate defining a pair ofReferences Cited parallel slots on the opposite side of said plate fromsaid legs and facing away from said plate for re- 5 UNITED STATESPATENTS ceiving the bottom edges of an inverted U-shaped 3,371,427 3/1968 yg 34155 housing to form cross-headers for conveying gas 3,453,7437/ 1969 Hale 34155 passing p y through said openings transversely EDWARDJ. MICHAEL, Primary Examiner

